The document discusses why overhearing mobile phone conversations in public can be annoying. It notes that most people believe others have bad mobile etiquette and many admit using their phones in public restrooms. Experiments found that overheard conversations were more annoying when people couldn't understand them, due to an innate human need to make sense of conversations. However, conversations that were more interesting or salient were less annoying to overhear, even if not understandable. The document concludes that the content and understandability of overheard mobile conversations significantly impacts how annoying they are perceived.